• The Korean Journal of Physiology and Pharmacology
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• 제25권3호
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• pp.227-237
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• 2021

Carbon monoxide (CO) is a cardioprotectant and potential cardiovascular therapeutic agent. Human cardiac fibroblasts (HCFs) are important determinants of myocardial structure and function. Large-conductance Ca2+-activated K+ (BK) channel is a potential therapeutic target for cardiovascular disease. We investigated whether CO modulates BK channels and the signaling pathways in HCFs using whole-cell mode patch-clamp recordings. CO-releasing molecules (CORMs; CORM-2 and CORM-3) significantly increased the amplitudes of BK currents (IBK). The CO-induced stimulating effects on IBK were blocked by pre-treatment with specific nitric oxide synthase (NOS) blockers (L-NG-monomethyl arginine citrate and L-NG-nitroarginine methyl ester). 8-bromo-cyclic GMP increased IBK. KT5823 (inhibits PKG) or ODQ (inhibits soluble guanylate cyclase) blocked the CO-stimulating effect on IBK. Moreover, 8-bromo-cyclic AMP also increased IBK, and pre-treatment with KT5720 (inhibits PKA) or SQ22536 (inhibits adenylate cyclase) blocked the CO effect. Pre-treatment with N-ethylmaleimide (a thiol-alkylating reagent) also blocked the CO effect on IBK, and DL-dithiothreitol (a reducing agent) reversed the CO effect. These data suggest that CO activates IBK through NO via the NOS and through the PKG, PKA, and S-nitrosylation pathways.

• BMB Reports
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• 제54권2호
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• pp.130-135
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• 2021

Voltage-gated potassium (Kv) channels are involved in many important cellular functions and play pivotal roles in cancer progression. The expression level of Kv2.1 was observed to be higher in the highly metastatic prostate cancer cells (PC-3), specifically in their membrane, than in immortalized prostate cells (WPMY-1 cells) and comparatively less metastatic prostate cancer cells (LNCaP and DU145 cells). However, Kv2.1 expression was significantly decreased when the cells were treated with antioxidants, such as N-acetylcysteine or ascorbic acid, implying that the highly expressed Kv2.1 could detect reactive oxygen species (ROS) in malignant prostate cancer cells. In addition, the blockade of Kv2.1 with stromatoxin-1 or siRNA targeting Kv2.1 significantly inhibited the migration of malignant prostate cancer cells. Our results suggested that Kv2.1 plays an important role as a ROS sensor and that it is a promising therapeutic molecular target in metastasis of prostate cancer.

• The Korean Journal of Physiology and Pharmacology
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• 제8권4호
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• pp.201-206
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• 2004

Mitochondrial ATP-sensitive potassium $(mitoK_{ATP})$ channels play a role in early and late ischemic preconditioning. Nevertheless, the subunit composition of $mitoK_{ATP}$ channels remains unclear. In this study, we investigated the subunit composition of $mitoK_{ATP}$ channels in mitochondria isolated from rat cardiac myocytes. Mitochondria were visualized using the red fluorescence probe, Mitrotracker Red, while $mitoK_{ATP}$ channels were visualized using the green fluorescence probe, glibenclamide-BODIPY. The immunofluorescence confocal microscopy revealed the presence of Kir6.1, Kir6.2 and SUR2 present in the cardiac mitochondria. Western blot analysis was carried to further investigate the nature of $mitoK_{ATP}$ channels. For SUR proteins, a 140-kDa immunoreactive band that corresponded to SUR2, but no SUR1 was detected. For Kir6.2, three bands $({\sim}44,\;{\sim}46,\;and\;{\sim}30\;kDa)$ were detected, and a specific ${\sim}46-kDa$ immunoreactive band corresponding to Kir6.1 was also observed. These observations suggest that the subunits of $mitoK_{ATP}$ channels in rat myocytes include Kir6.1, Kir6.2, and a SUR2-related sulfonylurea-binding protein.

• The Korean Journal of Physiology and Pharmacology
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• 제9권1호
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• pp.37-43
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• 2005

Our previous report demonstrated that chick myoblasts are equipped with $Ca^{2+}$-permeable stretchactivated channels and $Ca^{2+}-activated$ potassium channels ($K_{Ca}$), and that hyperpolarization-induced by $K_{Ca}$ channels provides driving force for $Ca^{2+}$ influx through the stretch-activated channels into the cells. Here, we showed that acetylcholine (ACh) also hyperpolarized the membrane of cultured chick myoblasts, suggesting that nicotinic acetylcholine receptor (nAChR) may be another pathway for $Ca^{2+}$ influx. Under cell-attatched patch configuration, ACh increased the open probability of $K_{Ca}$ channels from 0.007 to 0.055 only when extracellular $Ca^{2+}$ was present. Nicotine, a nAChR agonist, increased the open probability of $K_{Ca}$ channels from 0.008 to 0.023, whereas muscarine failed to do so. Since the activity of $K_{Ca}$ channel is sensitive to intracellular $Ca^{2+}$ level, nAChR seems to be capable of inducing $Ca^{2+}$ influx. Using the $Ca^{2+}$ imaging analysis, we were able to provide direct evidence that ACh induced $Ca^{2+}$ influx from extracellular solution, which was dramatically increased by valinomycin-mediated hyperpolarization. In addition, ACh hyperpolarized the membrane potential from $-12.5{\pm}3$ to $-31.2{\pm}5$ mV by generating the outward current through $K_{Ca}$ channels. These results suggest that activation of nAChR increases $Ca^{2+}$ influx, which activates $K_{Ca}$ channels, thereby hyperpolarizing the membrane potential in chick myoblasts.

• 대한약리학회지
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• 제25권1호
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• pp.53-58
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• 1989

본 연구실에는 최근 수년동안 말라리아, 성병등에 민간약으로 사용되어 온 회양목(Buxus microphylla var. koreana Nakai)으로 부터 다수의 물질을 분리하여 그 약리작용을 경색하여왔다. Coumarin의 유도체인 buxuletin은 이뇨 작용이 있음이 인정되었으며, steroid 성 alkaloid인 Cyclobuxine $D(C_{25}H_{42}ON_2)$는 항염증작용, 흰쥐에서 심박동수 감소작용 및 적출 평활근 이완 작용을 나타냈다. 본 연구에서는 회양목에서 Cyclobuxine D의 유도체인 Cyclobuxine $E(C_{24}H_{38}ON_2)$를 분리하여 그 구조를 이화학적인 방법으로 규명하였으며 흰쥐의 십이지장 평활근에서 acetylcholine에 의해 유도되는 수축 작용에 대한 영향과 높은 칼륨 이온에 의해 활성화되는 칼슘 채널에 대한 Cyclobuxine E의 영향을 관찰하였다. Cyclobuxine E는 적출 십이지장 평활근에서 acetylcholine의 수축작용을 현저히 억제하였으며, Calcium-depleted potassium-depolarizing 용액에 담근 후 $CaCl_2$를 가함으로써 나타나는 이중적인 수축작용을 용량적으로 차단하였다. 이상의 십이지장 평활근에 대한 Cyclobuxine E의 작용은 Cyclobuxine E가 칼륨에 의해 활성화되는 칼슘 채널 (아마, voltage-dependent calcium channel)을 통한 칼슘의 세포막 통과를 차단하므로 인해 나타남을 시사한다.

• The Korean Journal of Physiology
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• 제25권1호
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• pp.17-26
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• 1991

Single smooth muscle cells of the rabbit pulmonary artery were isolated by treatment with collagenase and elastase. Using the patch clamp technique, potassium channel activity was recorded from the inside-out membrane patch. The channel had a sin히e channel conductance of about 360 pS in symmetrical concentration of K on both sides of the patch, 150 mM, and had a linear current-voltage relationship. During the application of 10 mM tetraethylammonium (TEA) to the intracellular membrane surface, the amplitude of single channel current was reduced and very rapid flickering appeared. The open probability $(P_0)$ of this channel was increased by increasing positivity of the potential across the patch membrane, with e-fold increase by 20 mV depolarization, and by increasing the internal $Ca^{2+}$ concentration. These findings are consistent with those of large conductance Ca-activated K channels reported in other tissues. But the shortening of the mean open time by increasing $[Ca^{2+}]_i$, was an unexpected result and one additional closed state which might be arisen from a block of the open channel by Ca binding was suggested. The $P_0-membrane$ potential relationship was modulated by internal pH. Decreasing pH reduced $P_0$. Increasing pH not only increased $P_0$ but also weakened the voltage dependency of the channel opening. The modulation of Ca-activated K channel by pH was thought to be related to the mechanism of regulation of vascular tone by the pH change.

• 약학회지
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• 제41권4호
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• pp.399-406
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• 1997

The effects of different $K^+$ channel blockers were investigated on the non-adrenergic non-cholinergic (NANC) relaxations in the circular muscle of the rabbit proximal stomach. Non-selective blockers of $K^+$ channels, 4-aminopyridine (4-AP, 3~30${\mu}M$) and tetraethylammonium (TEA, 100~1000${\mu}M$) significantly enhanced the NANC relaxations in a concentration-dependent manner. The enhancement was more prominent for the NANC relaxations induced by the electric field stimulation (EFS) with lower frequencies. Blockers of large conductance $Ca^{2+}$-activated $K^+$ channels, charybdotoxin and iberiotoxin, a blocker of small conduntance $Ca^{2+}$-activated $K^+$ channels, apamin and a blocker of ATP-sensitive $K^+$ channels, glibenclamide had no effect on the NANC relaxations, respectively. Exogeneous administration of nitric oxide (NO, 1~30${\mu}M$) caused concentration-dependent relaxations which showed a similarity to those obtained with EFS. None of the $K^+$ channel blockers had an effect on the concentration-dependent relaxation in response to NO. These results suggest that prejunctional $K^+$ channels regulate the release of NO from the NANC nerve in the rabbit proximal stomach as the inhibition of prejunctional $K^+$ channels increases the NANC relaxation induced by the EFS.

• The Korean Journal of Physiology and Pharmacology
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• 제26권2호
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• pp.135-144
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• 2022

An antidiabetic drug, rosiglitazone is a member of the drug class of thiazolidinedione. Although restrictions on use due to the possibility of heart toxicity have been removed, it is still a drug that is concerned about side effects on the heart. We here examined, using Chinese hamster ovary cells, the action of rosiglitazone on Kv1.5 channels, which is a major determinant of the duration of cardiac action potential. Rosiglitazone rapidly and reversibly inhibited Kv1.5 currents in a concentrationdependent manner (IC₅₀ = 18.9 μM) and accelerated the decay of Kv1.5 currents without modifying the activation kinetics. In addition, the deactivation of Kv1.5 current, assayed with tail current, was slowed by the drug. All of the results as well as the usedependence of the rosiglitazone-mediated blockade indicate that rosiglitazone acts on Kv1.5 channels as an open channel blocker. This study suggests that the cardiac side effects of rosiglitazone might be mediated in part by suppression of Kv1.5 channels, and therefore, raises a concern of using the drug for diabetic therapeutics.

• The Korean Journal of Physiology and Pharmacology
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• 제2권2호
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• pp.133-145
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• 1998

$Ca^{2+}-signals$ in endothelial cells are determined by release from intracellular stores and entry through the plasma membrane. In this review, the nature of $Ca^{2+}$ entry and mechanisms of its control are reviewed. The following ion channels play a pivotal role in regulation of the driving force for $Ca^{2+}$ entry: an inwardly rectifying $K^+$ channel, identified as Kir2.1, a big-conductance, $Ca^{2+}-activated$ $K^+$ channel (hslo) and at least two $Cl^-$ channels (a volume regulated $Cl^-$ channel, VRAC, and a $Ca^{2+}$ activated $Cl^-$ channel, CaCC). At least two different types of $Ca^{2+}$-entry channels exist: 1. A typical CRAC-like, highly selective $Ca^{2+}$ channel is described. Current density for this $Ca^{2+}$ entry is approximately 0.1pA/pF at 0 mV and thus 10 times smaller than in Jurkat or mast cells. 2. Another entry pathway for $Ca^{2+}$ entry is a more non-selective channel, which might be regulated by intracellular $Ca^{2+}$. Although detected in endothelial cells, the functional role of trp1,3,4 as possible channel proteins is unclear. Expression of trp3 in macrovascular endothelial cells from bovine pulmonary artery induced non-selective cation channels which are probably not store operated or failed to induce any current. Several features as well as a characterisation of $Ca^{2+}$-oscillations in endothelial cells is also presented.

• 생명과학회지
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• 제14권5호
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• pp.882-890
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• 2004

간극결합(gap junction)은 이웃하는 두 세포사이에 형성된 막 구조물로 이를 통하여 각종 이온들과 여러 가지 분자들이 통과한다. 일반적으로 알려진 세포의 이온채널(예를 들어 $Na^{+}$ 이온채널과$K^+$이온채널)과 구별하여 두 세포사이에 형성된 간극결합을 세포간 채널(intercellular channel)이라고도 부른다. 간극결합채널(gap junction channel)은 단순히 수동적으로 열려있는 통로가 아니라 여러 가지 자극 즉 pH, 칼슘이온(calcium ion), 전압(voltage), 그리고 화학적인 변형(주로 인산화, phosphorylation)에 의해서 개폐(gating, opening and closing)가 조절되는 이온채널이다. 그 가운데서도 전압에 의한 간극결합채널 개폐 변화가 가장 많이 연구되었다. 세포안과 바깥에 형성된 전압차이(membrane potential, $V_m$) 보다는 주로 두 세포 사이에 형성된 전압차이(transjunctional voltage, $V_j$)에 의해서 간극결합채널은 민감하게 반응한다. 본 총설에서는 간극결합채널의 일반적인 특성을 정리해보고 전압-의존적인(voltage-dependent) 채널개폐에 관한 기전을 논의하고자 한다.